What If in Marxism

Slavoj Zizek, while discussing a book on alterntive histories makes some good points of the Marxist view on the "What If" histories and revolutionary action:

...it’s worth looking at how Lenin himself related to counterfactuality. He was as far as he could be from any reliance on ‘historical necessity’. On the contrary, it was his Menshevik opponents who emphasised the impossibility of omitting one of the stages prescribed by historical determinism: first bourgeois-democratic, then proletarian revolution. When, in his ‘April Theses’ of 1917, Lenin claimed that this was the Augenblick, the unique opportunity to start a revolution, his proposal was at first met with stupefaction or contempt by a large majority of his party colleagues. But he had understood that the opportunity was provided by a unique combination of circumstances: if the moment wasn’t seized, the chance would be forfeited, perhaps for decades. Lenin was entertaining an alternative scenario: what if we don’t act now? It was precisely his awareness of the catastrophic consequences of not acting that impelled him to act.